pracs Flashcards
How are metabolic reactions controlled by enzymes
Enzymes combine with the substrate molecule at the active site to produce a product
Structure of enzymes
Tertiary proteins where the polypeptide chain is folded back on itself into a spherical 3D globular shape
What are enzymes
Biological catalysts which speed up the rate of metabolic reactions
What is digestion
Large food molecules are digested by enzymes into smaller molecules and these products are then absorbed to the bloodstream
What is the active site
Where the substrate attaches to on the enzyme (groove in the enzyme)
What is a substrate?
Molecule that the enzyme breaks down into products
What is the lock and key theory
Enzymes are specific so the substrate is perfectly complementary to the active site
What enzyme is protein broken down by
Proteases
Where is protease found
Stomach, pancreas, small intestine.
What are proteins
Long chains of chemicals called amino acids
What happens when we digest proteins
The protease enzymes convert the protein back to the individual amino acids, which are then absorbed into the bloodstream
How are human proteins made
When amino acids are absorbed by the body cells they are joined together in a different order to make human proteins
Structure of the carbohydrate starch
Consists of a chain of glucose molecules
What are carbohydrates broken down by?
Carbohydrases
What carbohydrase breaks down starch
Amylase
What happens when carbohydrates like starch are digested
We produce simple sugars
Where is amylase found
In the saliva and pancreatic fluid
Structure of lipid
Molecule of glycerol attached to 3 molecules of fatty acids
What enzyme digests lipid molecules? And what does it produce
Lipase. Produces glycerol and fatty acids
Where is lipase found
Pancreatic fluid and small intestine
What else is involved in the digestion of lipids
Bile
Where is bile made and stored
Made in liver, stored in gall bladder
What does bile do
Speeds up the digestion of lipids but is not an enzyme
How does bile work
Converts large lipid droplets into smaller droplets (emulsifies the lipid) which increases S.A of lipid droplets and increases rate of lipid breakdown by lipase.
Why do we need to break down the biological molecules we eat (carbohydrates, proteins, lipids)
Normally pretty big molecules so too big to absorbed into bloodstream across villi of small intestine, so broken down to smaller pieces by enzymes
What does bile do to the small intestine
Creates alkaline conditions because it is alkaline so can neutralise stomach acid.
What is activation energy
Minimum energy needed to start a chemical reaction/energy needed to break existing chemical bonds
What do enzymes do to activation energy
Lower the activation energy of a reaction
Factors effecting rate of enzyme action
Temperature, pH, substrate concentration, enzyme concentration
What do buffers do
Maintain a constant pH
What are enzyme inhibitors
Inhibitor combines with enzyme and stops it from forming enzyme-substrate complex.
What are competitive inhibitors
Structurally similar to the substrate molecule so it can fit into active site instead of substrate
What are non-competitive inhibitors
Don’t bind to active site. Bind to allosteric site of enzyme and alters the overall tertiary structure of the enzyme molecule.
Function of small intestine in digestion
Digestion and absorption
Two regions of the small intestine
The duodenum and the ileum
How is the ileum adapted for absorption in humans
- Very long and lining folded to give large S.A.
- Folds have villi and on surface of villi are epithelial cells with microvilli. Increase S.A
- At base of villi are glands called crypts of Lieberkuhn and the epithelial cells of the crypts produce digestive enzymes which complete digestion.
Why do epithelial cells contain mitochondria
As ATP is needed for the active absorption of some of the products of digestion by active transport
Purpose of goblet cell in intestine
Produce mucus
Two features of columnar epithelium
- Mitochondria to produce ATP for active transport to help with digestion.
- Microvilli to increase S.A for diffusion. More space for molecules to diffuse in and out.
Why is the small intestine of a herbivore (rabbit) longer
Because herbivores have difficulty digesting cellulose so food takes longer to travel down the gut allowing more time for cellulose digestion.
Why is small intestine of a carnivore (cat) shorter
As protein is easy to digest.
